System for inflating balloons and injecting conductive reflectors therein



2,919,725 C' IING Jan. 5, 1960 H. J. MASTENBROOK SYSTEM FOR INFLATING BALLOONS AND mm CONDUCTIVE REFLECTORS THEREIN Filed Dec. 14, 1956 K 0 m0 NR B VN NE T S A M w Y W R N w E H W Y B O E F .QAHQ

ATTORNEYJ United States Patent SYSTEM FOR INFLATING BALLOONS AND IN- JECTING CONDUCTIVE REFLECTORS THEREIN Henry J. Mastenbrook, Falls Church, Va., assignor to the United States of America as represented by the Secretary of the Navy The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates generally to radar reflectors and more particularly to a means for inflating a balloon and applying conductive reflectors to the inner surface of a balloon.

Previous attempts to utilize radio frequency energy reflectors to obtain meteorological data have envisioned the use of rubber-like balloons partially encased in a material capable of reflecting radio frequency energy. In order for the material to remain on the balloon, more than half the surface area of the balloon is required to be encased. This limits the amount of volume expansion ofthe balloon to the expansion of the casing, which is considerably less than that of the balloon itself. Therefore, the maximum altitude such as a balloon can attain is limited. Consequently, wind velocities capable of being measured at high altitudes by the conventional theodolite method during periods of good visibility can only be obtained at lower altitudes in any kind of weather using such a type of balloon and radar equipment.

Another prior art device embodies a hemispherical balloon mounted on an equatorial plane surface of radio frequency energy reflective material with vanes extending from the outer surface of the balloon. These vanes cause the balloon to rotate upon rising in the atmosphere, thereby causing the reflective material surface to remain on the bottom of the balloon. This device also fails to attain the maximum altitudes obtainable by the balloons normally used in conjunction with theodolites.

Another prior art device is disclosed in Patent Num:

ber 2,752,594 in which a plurality of small metallic resonant dipole elements are applied to the inner surface of a conventional meteorological balloon in sufficient quantities to have these dipole elements present a substantially non-directional reflective surface to radio frequency energy. These dipole elements can be attached to either the exterior or the interior surface of the balloon by means of a non-rigid yielding or fluid adhesive cementitious material.

In the reflector type balloon of Patent No. 2,752,594 it is difiicult to uniformly apply the small dipoles to the surface. The present invention overcomes this shortcoming and provides an eflicient device for injecting the dipole particles into the balloon whereby the dipoles more readily adhere to the inner surface of the balloon and uniformly distribute themselves over the inner surface.

It is, therefore, an object of this invention to provide a device for inflating a balloon and distributing resonant dipoles about the inner surface thereof to form a radar reflector.

Yet another object is to provide a device for more equally and uniformly distributing many dipoles over the inner surface of a balloon.

A further object is to provide a simple device whereby inexperienced personnel may inject dipole elements into a balloon and obtain consistently good distributions of dipole elements about the inner surface of the balloon.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawings in which:

Fig. l is a side view of the device of this invention which is cutaway at one end to illustrate a cylinder therein loaded with resonant aluminum dipole elements;

Fig. 2 is an end view of the device along line 2-2 of Fig. 1;

Fig. 3 illustrates a schematic drawing of a rotatable three way valve used with the device; and

Fig. 4 illustrates a cross-sectional view of a balloon with the inner surface coated with dipole elements.

The device of the present invention is a combination inflation nozzle and dipole injector which comprises an elongated cylinder that has a cylindrical chamber which may be charged with a cylindrical packet of dipole elements and a separate tubular passage extending through the cylinder parallel to the chamber to form the inflation nozzle for the passage of a gas. One end of the device is inserted into the neck of a ballon, and the ballon is filled with a gas through the tubular passage, then gas pressure is applied to the packet of dipole elements in the chamber along the axis of the chamber which forces .the dipoles from the packet and into the ballon whereby the dipole elements adhere to the inner surface of the balloon which has been treated with an adhesive material.

Referring now to the drawings, the device illustrated in Fig. 1 is an elongated cylinder or housing 10 which comprises a cylindrical chamber 11 closed at one end with an axially disposed air inlet 13 connected thereto, said chamber extending longitudinally of said elongated cylinder to an open end and a tubular by-pass passage 12 in said housing parallel to the longitudinal axis of the cylindrical chamber. Appropriate gas lines 13 and 14 extend from a three-way valve 15 and connects respectively to the cylindrical chamber 11 and the tubular passage 12 for the purpose of supplying a gas separately thereto through inlet 16. As shown, the cylindrical chamber has a charged cylindrical packet 17 therein which extends the full length of the chamber and contains several layers of dipole elements 18 stacked in end to end relationship as partially shown in Fig. 1 and held in the packet by pressure of the elements against each other and the chamber wall. When the chamber is loaded with a packet of dipole elements, a rupturable' moisture proof diaphragm such as aluminum foil 21 is adapted to be fixed over the open end of the chamber and held in place by a retaining ring 22 which is threaded on the inner surface for threading onto the cylindrical chamber. The retaining ring also holds the dipolepacket in the chamber.

The end view of the device is illustrated in Fig. 2 and shows the relationship between the cylindrical chant ber 11 and by-pass 12.

Fig. 3 is a schematic of the three-way valve 15 having a rotatable T-shaped passage therein. Valve 15 is shown in the off-position, when the valve is rotated 45 in the direction of the arrow, gas is supplied from the inlet 16 through passage a, b, through gas line 14 and to" by-pass 12, from that position, when the'valve is rotated in the direction of the arrow passage b, 0, lines the inlet 16 with the line 13 to the cylindrical chamber 11; This arrangement provides a system for supplying gas Lhrough either the by-pass 12 or to the cylindrical cham- Fig. 4 illustrates a balloon 23 shown in a sectional view with the inner surface covered with dipole elements such as supplied by the device of the present invention shown by illustration in Fig. 1. These elements are oriented with respect to the surface of the balloon in a random manner as shown in Fig. 4 and are attached to the balloon 23 by means of a yielding cementing material 24 such as liquid latex or other rubber cement. Metallic elements 18 are preferably so dimensioned that their longest dimension equals approximately a half wavelength of the frequency to be used, thereby enabling the metallic elements to behave as half-wave dipoles. For example, for use with 3 cm. wavelength energy, metallic elements 1 should be 1.5 cm. in length. However, while the use of metallic elements 18 as dipoles is preferable, results can be obtained if enough metallic particles are attached to the balloon to enable the balloon to act as a substantially spherical reflective surface regardless of the wavelength used.

In a typical practical embodiment of the present invention, a balloon originally inflated to a diameter of 5 feet at a ground station and which is to be tracked by a radar transmitter transmitting 3 cm. wave energy is equipped with about 500,000 particles of metal foil, for example, aluminum. Each of these particles has a length of approximately 1.5 cm., thereby enabling it to act as a dipole reflector. The other dimensions are made as small as possible such as 8 mils wide and a thickness of 4.5 mils. These particles are applied to the balloon inner surface by first coating the inner surface with a cementitious coating 24 of any suitable substance having adhesive qualities and a low freezing point such as ethylene glycol and then injecting the dipole elements 18 into the balloon by the device illustrated in Fig. 1.

The cementitious coating 24 is applied by pouring the coating substance into a deflated balloon and forcing the substance along the full length as by pulling the balloon through a partly closed hand. After applying the coating, the excess cementitious substance is poured from the balloon and one end of a charged dipole injector device is inserted into the neck of the balloon. With the valve 15' in the off-position, the inlet end of the valve 15 is connected to a pressurized tank of low density gas such as helium and the valve is turned on to allow gas to enter the balloon under pressure through the by-pass 12 until the balloon is taut. The valve is then turned 90 to line up the gas inlet with the cylin drical chamber 11 to apply pressure to the dipole chamber. When the pressure becomes great enough, the dipole elements are forced from the charged packet rupturing the diaphragm 21 and the individual dipole elements 18 are injected into balloon, then the valve is closed, the injector device is removed and the neck of the balloon is sealed.

The dipole elements upon striking the balloon inner surface, which has been previously coated with a cementitious substance, adheres to the inner surface in a random distribution. Some of the dipole elements will hit others when injected and will fall toward the bottom surface of the balloon, the balloon can be revolved slowly about its axes and those loose dipole elements Will find a space to which they will adhere to the inner surface of the balloon. The weight of the metallic particles is negligible compared to that of the ballon so that it does not appreciably affect the maximum altitude attainable by the balloon, since the amount of expansion of the balloon depends upon the outside pressure of the atmosphere. Since only a few ounces of weight are added to conventional balloons by the addition of the dipoles compared to large additional Weights inherent in prior art devices, the rate of rise of the present device is substantially unimpeded. Hence, higher altitudes can be studied for any given maximum range at which echoes are obtainable.

The metallic particles do not appreciably affect the burst ing point of the balloon. Therefore, the balloon embodied in the present invention is able to rise to levels comparable with that reached by conventional meteorological balloons and since it can be tracked by radar devices, is not limited in its operation to periods of good visibility.

While optimum results are obtained using dipole elements having lengths such as to enable them to resonate at the frequency of the energy to be reflected, namely, approximately a half-wave length, echoes can be obtained from non-resonant lengths of metal foil. However, it is preferable for best results to have the dipole length such that it will resonate. This enables the range at which reflections are obtained by an observer tracking the balloon by radar to be increased to a maximum.

The injector device is not limited to round balloons as shown in Fig. 4 but may be used to apply dipole elements to the inner surface of balloons having any shape and any type of balloon can be used such as expansible or non-expansible.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It ist herefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A combination balloon inflation nozzle and dipole element injector which comprises an elongated housing, a chamber extending longitudinally of said housing, said chamber being closed at one end with a gas pressure line connected axially thereto to permit a gas flow into said chamber, said chamber being open at the opposite end for receiving a packet of said dipole elements, means for retaining said packet in said chamber, a by-pass extending through said housing parallel to the longitudinal axis of said chamber and valve means for controlling a supply of gas under pressure respectively to said by-pass for inflating a balloon and to said chamber for injecting said dipole elements into said balloon through said open end of said chamber.

2. The combination as claimed in claim 1 wherein a rupturable diaphragm is secured over the open end of said chamber.

3. A combination balloon inflation nozzle and dipole injector which comprises an elongated cylindrical housing, a cylindrical chamber extending longitudinally of said housing, said chamber being closed at one with a gas pressure line connected axially thereto to permit a gas flow into said chamber, said chamber being and open at the opposite end for receiving a packet of said dipole elements, means for retaining said packet in said chamber, a rupturable diaphragm secured over the open end of said chamber, a cylindrical by-pass extending through said housing parallel to the longitudinal axis of said chamber and valve means for controlling a supply of gas under pressure respectively to said by-pass for inflating a balloon and to said chamber for injecting said dipole elements into said balloon through said open end of said chamber.

References Cited in the file of this patent UNITED STnTES PATENTS 1,258,104 Gadsden Mar. 5, 191.8 1,494,709 Roberts May 20, .1924 1,495,487 Johnson May 27,, 1924 2,187,376 Guibert Jan. 16, 1940 2,675,147 Odom Apr. 13, 1954 2,767,796 Roberts Oct. 23, 1956 2,856,010 Brill et al Oct. .14, 195.8 

